Electrochromic safety glazing

ABSTRACT

An electrochromic device is achieved that exhibits the characteristics of impact-resistant safety glass by subjecting a solid electrolyte sheet material and a peripheral sealant material sandwiched between substrates to heat and pressure such that the electrolyte bonds to the surfaces of the substrates with an adhesion of at least 1.8 kg/linear cm width causing the electrolyte to exhibit a tensile strength of at least 5 kg/cm 2 .

REFERENCE TO PRIOR APPLICATION

This application claims the benefit under Title 35 United States Code§119(e) of the provisional application Ser. No. 60/286,105 filed Apr.24, 2001.

FIELD OF THE INVENTION

This invention relates to electrochromic glazing and, more particularly,to such devices for safety glazing applications.

BACKGROUND OF THE INVENTION

Electrochromic (EC) devices have many applications, some of them areautomotive mirrors, car glazing including sunroofs, glazing for othertransportation means such as boats, planes, trains, buses, etc., and forarchitectural glazing applications for interior and exterior uses.Briefly, EC devices are made by sandwiching an electrolyte between twocoated substrates. Many examples of such devices are shown in U.S. Pat.No. 6,317,248 which is incorporated herein by reference. To operatethese devices electrical power is applied across the electrolytecross-section via the coatings on the substrate, so that a movement ofthe charged species (ions or polarized particles) takes place. Theseions are transported via the electrolyte to the electrode surfaces forfurther reactions to take place which gives rise to color change orchange in optical density. This change is varied reversibly at thediscretion of the user. As used herein, the terms electrochromic devicesare intended to also include devices in which polarized particles arenot transported across the electrolyte for a color change, but insteadsimply re-orient themselves as in liquid crystal devices and suspendedparticle devices. In addition, other user controlled variabletransmission devices employing similar principles of construction, i.e.,an active material sandwiched between the two substrates, such as “usercontrolled photochromic devices” are also intended to be embraced bythese terms. Such laminates may also be incorporated in window systemswhere additional glass elements are used (e.g., insulated glass units)where these additional elements may not be laminated.

While it is conventional practice in electrochromic devices to use aliquid electrolyte or a solid electrolyte, as shown, for example in U.S.Pat. Nos. 6,1534,306 and 5,856,211, such prior approaches have notresulted in an electrochromic device that exhibit safety characteristicscommon to conventional (non-electrochromic) laminated glasses such asthose made by laminating polymeric sheets Safelex™ (Solutia, SaintLouis, Mo.) or Butacite™ (Dupont, Wilmington, Del.). Safety, in thecontext of applicable building industry and automotive industrystandards, is defined not simply as preventing leakage of theelectrolyte leakage from a broken laminate, but containment of thepieces of broken glass to avoid injury to the occupants in case of animpact.

One might suppose that it would be straight-forward to produce anelectrochromic device that could exhibit the attributes of safetyglazing by interposing between the substrates a polymeric sheet forglass lamination such as those made of polyurethane, PVC orpolyvinylbutyral, including Butacite™ from Dupont and Safelex™ fromSolutia. However, an electrochromic device requires chemically activecontact between the electrolyte and the coated surfaces of thesubstrates which would be prevented by such ordinary plastic sheetswithout modification. Modification, such as addition of plasticizers bysoaking could compromise their ability to impart safety attributes.Accordingly, it would be advantageous to achieve an electrochromicdevice that would exhibit the characteristics of impact-resistant safetyglass. Moreover, a mandated use of tempered glass would not besatisfactory as it limits the type of transparent conductors and othercoatings that can be used with electrochromic devices. Assembled ECdevices made of glass substrates may be laminated with external sheetsof polymeric material, such as Spallshield™ (Dupont, Wilmington, Del.)to yield impact resistant laminates. However, these post processesincrease cost and the scratch resistance of the polymeric sheets isusually not as good as glass.

SUMMARY OF THE INVENTION

In accordance with the principles of the present invention anelectrochromic device is achieved that exhibits the characteristics ofimpact-resistant and scratch resistant safety glass without requiringthe use of additional plastic laminates or tempered glass. We havediscovered that such a device can be achieved by using a solidelectrolyte sheet material, such as that described in EP 1056097, and bysubjecting the assembly to heat and pressure in situ such that theelectrolyte bonds to the treated surfaces of the glass substrate usedfor electrochromic devices with an adhesion of at least 1.8 kg/linear cmwidth, the electrolyte exhibiting a tensile strength of at least 5kg/cm².

Briefly, EP 1056097, discloses a solid electrolytic material having apolymeric binder selected from the group consisting of poly-acrylate,polystyrene, polyvinyl butyral, polyurethane, poly vinyl acetate, polyvinyl chloride and polycarbonate, a filler (such as polymer particles orpyrolitic silica, alumina, cerium oxide and zinc oxide), at least onedissociable salt (such as LiClO₄, LiCF₃SO₃, LiN(CF₃SO₂)₂, NaCF₃SO₃), atleast one solvent for dissociating the salt (propylene carbonate,ethylene carbonate, gamma-butyro lactone, tetraglyme, sulfolane), andother additives (such as antioxidants and UV stabilizers).

To make the electrochromic safety glazing, the solid electrolytic sheetmaterial is cut to size and placed between the two glass substrateshaving their coated surfaces (and for some types of EC devices, at leastone of the surfaces is a reduced surface layer) facing the electrolyticsheet. The substrates are advantageously staggered in the busbar areaswith the busbar on the two substrates along the two opposite edges, andthe sheet preferably extends only to the coated area (i.e., does notextend on to the etched area or to the end of the substrate perimeter.The assembled device is then sealed in a vacuum bag (and a vacuum ispulled to degas). The assembled device is then subject to heating andpressure such as in an autoclave at 130° C. and 200 psi for 1 hr with 45min ramp time to adhere the polymeric electrolyte to the substrates. Thepressure is maintained after the completion of the heating cycle andafter the samples have cooled down to 60° C. or lower.

BRIEF DESCRIPTION OF THE DRAWING

FIGS. 1a through 1 c show 3 different types of EC constructions;

FIGS. 2a and 2 b show fabrication of an electrochromic device accordingto the invention which exhibits the characteristics of safety glass;

FIGS. 3a, 3 b and 3 c show fabrication of an alternative form ofelectrochromic device according to the invention; and

FIGS. 4a and 4 b show top and side views of a substrate with atransparent conductor and busbar deposited on the transparent conductorthat may be used in the embodiments of FIGS. 2 and 3.

DETAILED DESCRIPTION

FIG. 1a shows the type of construction illustrated e.g., in U.S. Pat.No. 5,910,854, where all of the electrochromic activity takes place inan electrolyte positioned between transparent conductors. Suchelectrolytes may include liquid crystals or particles which align in theelectric field imposed by electronic charging of the opposingelectrodes. FIG. 1b shows a type of construction illustrated byWO97/38350 in which the electrolyte is positioned between a transparentconductor and an electrochromic electrode layer. FIG. 1c shows yetanother type of electrochromic device, such as shown, e.g., in U.S. Pat.No. 6,266,177B1 where the electrolytic layer is situated between anelectrochromic layer and an ion-storage electrode, where the ion-storagelayer may also exhibit electrochromic properties. If the devices ofFIGS. 1a through 1 c were to exhibit characteristics desired of safetyglass, the electrolyte must bond to the transparent conductors withoutsacrificing its electrochromic abilities and must remain bonded theretoeven after impact fracture. In the type of construction illustrated inFIG. 1c, to exhibit the characteristics of safety glass, an electrolytemust be used which will bond to the electrochromic layer and to the ionstorage layer of the substrates and remain bonded thereto after impactfracture.

FIGS. 2a and 2 b show the process of laminating the construction of FIG.1c between substrates S1 and S2. A free standing electrolytic film sheetEF, having the appropriate characteristics mentioned above, is placed onthe lower substrate LS1 which has deposited thereon a transparentcoating TC1 and an ion storage layer ISL. Above the electrolytic filmsheet EF the second substrate S2 is placed so that its electrochromiclayer ECL faces film sheet EF. The second substrate S2 has its owntransparent conductive coating layer TC2 The parts shown in FIG. 2a areplaced between heated rollers (or in an autoclave) resulting in theadhesion of electrolytic film sheet EF both to the electrochromic layerECL of the upper substrate S2 and to the ion storage layer ISL of thelower substrate S1. The assembly may have to be subjected to evacuationof trapped air before the simultaneous application of heat and pressure.

FIGS. 3a through 3 c show the lamination of an EC device which hasbusbars B1, B2 and B3, B4 deposited on respective transparent conductivelayers TC2 and TC1, advantageously as a silver frit pattern such asdisclosed in copending U.S. application Ser. No. 09/565,999. In FIG. 3aa bead sealant BS is applied about the periphery of electrolyte filmsheet EF and the parts are placed between heated rollers (not shown) andlaminated together to form the subassembly shown in FIG. 3b. Sealant BScan be an adhesive dispensed on one of the substrates, it could be atape, or a “picture” frame form cut out of a sealant material. Afterprocessing, electrical leads T1, T2 are connected to the busbars byconductive adhesive, soldering or mechanical clamping.

FIGS. 4a and 4 b show the layout of the busbars such as B3 on atransparent conductor layer TC1. a configuration of busbar on thetransparent coating. The busbar can be a tape, a frame cut out of asheet, or a frit (such as silver frit from Dupont Electronic Materials(Wilmington, Del.) thick film composition product number 7713 and Ferro(Santa Barbara, Calif.) silver paste FX33-246), or a conductiveadhesive, such as a silver filled epoxy.

In the aforementioned structures, the transparent conductors may be usedwhich can be selected from the group consisting of Indium-tin oxide orfluorine doped tin oxide which may be deposited directly on thesubstrates, or they may be deposited on anti-iridescent or barriercoatings such as an SiO₂ coating on soda-lime glass which may alsoreduce the sodium diffusion from the substrate into the device. Theelectrochromic layer may be either organic or inorganic. Some examplesof inorganic electrochromic coatings are tungsten oxide, molybdenumoxide, mixed oxides comprising tungsten or molybdenum oxides, andexamples of organic EC materials are polyaniline, polythiophene, andtheir derivatives, among which polyethylenedioxythiophene and itsmodifications should be noted. The ion-storage layers may be any of thefollowing, iridium oxide, nickel oxide, manganese oxide and vanadiumoxide, titanium-vanadium oxide and titanium-cerium oxide,niobium-vanadium oxide and mixtures comprising any of these oxides.

In FIG. 1a, the electrolyte will contact only the transparent conductor,whereas in FIG. 1c, the electrolyte will contact both the EC electrodeand the ion-storage layer. Thus, an electrolyte with good adhesion for adevice in FIG. 1a may not be suitable for the device in FIG. 1c from anadhesion standpoint because the substrates the electrolyte is in contactwith are different. We have discovered an electrolyte and a processwhich will successfully bond when subjected to heat and pressure to eachof the surfaces of the substrates of FIGS. 1a through 1 c.

Adhesion is typically measured by a peel test (e.g., ASTM D3167). At 90degree peel angle between the laminated substrate and the film which isbeing pulled, the adhesion should withstand a pulling force preferablygreater 1.8 kg/linear-cm width. This is important in an impact test,because too low an adhesion can release glass pieces from the laminatewhich are bigger than 1 sq inch (645 sq mm) and hurt the occupants. Toimprove the adhesion of the electrolyte film to the substrate coatings,one may add additives to the electrolyte or/and apply a adhesionpromoting primer (e.g., silane based) to the electrode area, e.g., by adipping or a vapor process.

In accordance with the invention, the electrolyte material disclosed inEP 1056097 is used as the electrolyte in any of the EC devices of FIGS.1a through 1 c by subjecting the device to heat and pressure in situ soas to cause the electrolyte to adhere to the respective layers orsurfaces of the substrates with an adhesion of at least 1.8 kg/linear cmwidth and to exhibit a tensile strength to breakage of at least 5 kg/cm²and an elongation to failure of 100%. Exemplary electrolytic materialsof the above type have been produced by BASF (Ludwigschafen, Germany)with the nomenclature EK 10 and EK 64.

Electrolytes for strength are measured without laminating plates. Iflamination process changes properties by increasing consolidation,reactions (including polymerization), the laminate can be formed usingrelease layers so that the electrolyte can be tested after laminationprocess. Peel is measured by laminating to only one rigid substrate. Theother side has to be removed, thus it is preferred to use release layerson one side. A laminate such as a complete EC device when formed is onlytested for impact tests.

The aforementioned electrolyte consists of at least one polymeric binder(such as poly-acrylate, polystyrene, polyvinyl butyral, polyurethane,poly vinyl acetate, poly vinyl chloride and polycarbonate), a filler(such as polymer particles or pyrolitic silica, alumina, cerium oxideand zinc oxide), at least one dissociable salt (such as LiClO₄, LiCF₃SO₃, LiN(CF₃ SO₂)₂, NaCF₃ SO₃), at least one solvent for dissociatingthe salt (propylene carbonate, ethylene carbonate, gamma-butyro lactone,tetraglyme, sulfolane), and other additives (such as antioxidants and UVstabilizers. Compatible monomers of the polymers described above orothers which further polymerize and/or crosslink may be added to enhancethe strength of the electrolytic film or its adhesion to the substratesduring the processing of the film itself and/or during the processing ofthe EC device. Adhesion promoters such as silanes or other ionicpolymers may be added. Further, this mixture is made in a consistency sothat it is extrudable into sheets. The fillers are either matched inrefractive index to the polymer binder or their size is smaller than thewavelength of light so that the scattering of light (haze) is kept to aminimum.

The electrolytic film that is to be incorporated in the EC device ispreferably extruded so that it may or may not have a uniform compositionthroughout its cross-section. For example, a film may be prepared bylamination or extruded with three separate regions, a core and a skinlayer on either side. The two outer skins of the film (which itself mayconsist of more than one layer) may have different composition so thatthe adhesion to the substrates can be further enhanced, and/or these mayprovide better processability, and/or may impart better UV blockingproperties. Typically these skins will have good adhesion to the coreand will typically comprise less than 20% of the total cross-sectionalthickness. The composition of the skin and the core could generally bethe same as described above, or only one of them may have thiscomposition. This is particularly suitable for devices which may havethe liquid crystal material or suspended particles only in the coreregion.

In the EC devices of this invention, all thin coatings such as thetransparent conductors, electrochromic layers and ion storage layers arepre-deposited on the substrates which are being laminated to theelectrolytes. There may be other layers which may be deposited on thesubstrates such as UV absorbing, dielectrics and protective coatingssuch as additional ion-conductive coatings. When a peel test isconducted between the electrolyte and the substrate, it is importantthat the failure does not occur in any of the other underlyinginterfaces or layers. Another important advantage of laminated glazingis the noise reduction which is transmitted from the outside to theinterior cabin. Since, the EC devices of this invention have mechanicalcharacteristics comparable to laminated glass, these devices are alsocapable of reducing sound transmission. While human ears are sensitivein a range of a few Hz to about 20,000 Hz, for most road and wind noisean important frequency range is between 100 Hz to about 8000 Hz. Theviscoelastic and shear properties of the electrolyte along with thestructural properties of the laminate should dampen the vibrations inthis range. Since the properties of the polymers are temperaturedependent, these benefits should hold in the temperature range of use,which is application dependent. Making the laminate using the two glasssheets in different thickness reduces the noise further, as thecharacteristic frequency of vibration of the two plates is thendifferent. For automotive applications desired thickness of EC laminatesis preferably less than 7 mm, and more preferably less than 5 mm to keepthe weight under control. However, for special applications such asarmored cars different guidelines may apply. A desired reduction innoise in the range of above mentioned frequencies is 3 dB or more, andmore desired noise reduction is greater than 5 dB. This reduction iscompared to a monolith sheet of substrate (e.g. glass) which isequivalent in thickness to the two substrates. For buildings, glass israted as “sound Transmission Class” (STC) as measured by ASTM E90 testor equivalent. For example STC of a laminate formed by two ⅛^(th) thickinch glasses with a Saflex™ layer of 0.03 inch increased the value to 35from 31 for a ¼ inch thick glass. Since, the EC windows of thisinvention can provide more benefits to the user other than the controlof light it is easier to justify their cost premium. The windows of thisinvention may further be used in complete window constructions such asintegrated glass units.

In making electrochromic glazing there are a number of important factorsthat should be considered in addition to the adhesion and tensilestrength of the electrolyte. Among these are the following, notnecessarily in order of importance: Ionic conductivity or particlemobility (electrical property); optical properties; UV stability;temperature stability; processability; and ionic conductivity:

The charged species (or ions, e.g., H+, Li+, Na+and others depending onthe device type) are transported through the electrolytes, thus in orderfor these devices to function the electrolytes should have a desiredionic conductivity. A preferred conductivity range at room temperature(25C) is 10⁻⁶ S/cm or greater. Since in some cases the use temperatureextreme may be between −40 to 105C, it is desired that in most of thistemperature range i.e., above 0C their conductivity does not drop below10⁻⁸ S/cm, more preferably below 10⁻⁷ S/cm. For example, an electrolytewith a conductivity of less than 10⁻⁸ S/cm at or below 0C may result ina device with slow kinetics, and may not be acceptable for anapplication where this needs to operate at low temperatures. Typically,the conductivity of the electrolyte decreases as the temperature islowered. For field devices a measure of particle mobility is made byimpedance measurements in a range of frequencies rather than ionicconductivity.

Optical Properties

The optical properties that are important for such application includeoptical transmission and haze. The electrolyte film may appear hazy dueto a surface texture, but the quality of haze should be tested aftermaking a laminate with clear glass substrates. The exceptions could beliquid crystal devices where a 2^(nd) component of a differentrefractive index is added to the electrolyte, and the electronicactivation of the device switches between clear and opaque states. Thehaze for most devices should be as low as possible and the optical(photopic) transmission as high as possible. Typically when such filmsare laminated between two substrates, their visible optical haze shouldbe lower than 5%, and more preferably less than 2%. The intrinsic hazein the film can be measured by laminating a film of the electrolytebetween two haze free substrates such as clear float line glass or clearglass with transparent coatings on it (haze free substrate are definedas substrates having a haze value lower than 0.2%). Haze of the laminateis then measured using ASTM test method D003 by using a spectrometersuch as Ultrascan XE made by Hunterlab (Reston, Va.).

The electrolyte may have other additives to reduce the near-infra-redradiation transmission (typically between 700 to 2500 nm) or to add atint to obtain a desired color.

These haze numbers and the optical properties should be maintained inthe temperature range of intended use. The optical properties of the ECdevice will depend on several factors in addition to the electrolyteproperties, some of these are substrate and electrode colors and thechange in the electrode or electrolyte color due to the electrochromicaction. Further, substrates can be polymeric or glass. The glass windowscould be bent, toughened, tempered, and may have busbar patterns toaddress individual sections. All of these topics are discussed in detailin PCT patent application WO01/84230 which is incorporated herein byreference. The electrochromic panels formed by using these electrolytescould have a wide range of color and modulation. Typically, the ECwindows of interest will have a photopic contrast or contrast at 550 nm(bleach state transmission/colored state transmission) in excess of 2:1and more preferably in excess of 3:1 and most preferably greater than5:1.

The degradation of the optical properties of the EC function, i.e.,clear state transmission, bleached state transmission and the speed ofchange from one state to the other should be within 20% and morepreferably within 10% before and after tests such as Temperature and UVtests described below. In addition, the color shift in any of the statesshould be minimum, so that it is not easily apparent to a user todistinguish a tested panel from the one not tested by means of colordifferences.

UV Stability:

The electrolytes for chromogenic devices will likely be used inapplications where they are subjected to the UV radiation, either fromthe sun or other light sources. In addition, it is preferable that theelectrolyte itself be resistant to UV in the range of 290 to 400 nm, andalso be stable to visible light exposure. Further, it is preferable thatthe electrolyte absorb UV so that chromogenic windows largely filter outthis radiation before it reaches the occupant. One test to check the UVresistance is via a continuous UV exposure using a weatherometer. Thistest is described in the test-procedure SAE J1960 (SAE is Society ofAutomotive Engineers, Warrandale, Pa.), where black panel temperature is70C. To accelerate the test further, one could increase the UV intensityand/or increase the black panel temperature. We have typically usedeither the SAE test or a higher black panel temperature of 85C. Tomeasure the UV stability in the laminate configuration described above,the SAE J1960 protocol may be used together with subjecting the sampledirectly to the required UV intensity under dry conditions to give anexposure of 2500 kJ of UV as measured with a 340 nm band-pass filter.After this exposure, the properties (optical, mechanical and electrical)should still be within the specs listed in the other sections.

Temperature Stability:

The electrolyte must maintain its properties within the temperaturerange of use. Further, once the electrolyte is laminated into achromogenic system, it may be subjected to temperatures higher than theuse temperatures during further processing, such as edge sealing,encapsulation, integration with other components, etc. Thus, it isdesirable that such electrolytes be chemically stable about 15° C. ormore above their maximum use temperature, more preferably, 50° C. ormore above their maximum use temperature, for at least 2 hours andpreferably for more than 24 hours. Other temperature tests may bedesigned where glazing may be subjected to prolonged periods of elevatedtemperature, low temperature and cycled between the temperatureextremes. Humidity is also used in test procedures, however, it is moreof a function of seal integrity. Some of these tests can be found inAgrawal A., Lampert C. L., Nagai J., Durability Evaluation ofElectrochromic Devices—An Industry Perspective, Solar Energy Materialsand Solar Cells, 56 (1999) 449; Lynam N. R., Agrawal A., AutomotiveApplications of Chromogenic Materials, in Large Area Chromogenics:Materials and Devices for Transmittance Control. Lampert C. M.,Granqvist C. G., eds. SPIE, Optical Engineering Press, Bellingham, Wash.(1990) 46.). This means that after such exposure the optical, mechanicaland electrical properties should still be within the specifications.

Processability

Processability is an important aspect in handling the electrolyte filmto be employed in an EC device. It is of course desirable to keep theelectrolytic film away from contacting moisture and oxygen (air) and, tothis end, it may be desirable that the film when extruded besimultaneously packaged with protective release films on both side.Extrusion along with compounding (mixing) is a standard plastic sheetingmanufacturing method, and more information can be found in PlasticsMaterials and Processing, by A. Brent Strong, Prentice Hall, UpperSaddle River, N.J. 1999. In those cases where the components are to bemixed well, a twin-screw extruder is used. Appropriate protective filmsto provide a barrier against moisture, oxygen and migration ofelectrolytic constituents from migrating to the outside includepolyolefin (polyethylene, polypropylene, copolymers) and polyester suchas polyethylene terephthalate, etc. Further, it is preferred that afterthe protective films are in place the resulting composite is passedthrough embossing calendars or similar equipment which may result in asurface texture similar to the Safelex™ and the Butacite™ laminationfilms. This ensures that during lamination gas bubbles at theelectrode/electrolyte interface can be extracted easily during thelamination process. To have better barrier the protected films may berolled or cut to sized and packaged in metallized or other bags or cansfor transportation. In the EC assembly operation, the bags containingthe electrolyte are preferably opened under dry conditions where thesheets are cut to size although they may be briefly handled in air or aninert atmosphere when the protective covers are peeled off. As is wellknown, a seal is used at the edges of the substrate. The substrate(device) edges may be sealed after the assembly is subjected to heat andpressure to bond the electrolyte to the substrates (the laminationprocess). Alternatively, the electrolyte film may be placed on one ofthe substrates along with a bead of the seal around the periphery of theEC device. During the lamination process, the seal also cures, and acomplete EC assembly is obtained in one process. In any of these asecondary seal may be applied to give better hermetic properties to theseal.

One may also use a process where an edge seal is simultaneouslyco-extruded along with the electrolyte sheet. Since, extrusion is acontinuous process, one will have to use one of the above describedmethods to cover the device edges which are perpendicular to thedirection of extrusion. An additional step of UV radiation exposure mayhave to be introduced to further cure the sealant and/or theelectrolyte.

EXAMPLE 1

An electrolyte was made according to the teaching of this applicationwith the following composition in which as EK 10 and EK 64 are exemplaryexperimental materials produced by BASF following the teaching of EP1056097.

EK10 30% UV 27.7% Tetraglyme 5.3% LiClO₄ 37% fumed SiO₂ stabilized PMMA

The above electrolyte was laminated between two 2″×2″ Tec 15 glass platesubstrates (conductive side facing inwards) as described below:

1. Out of substrate stock, two 2″×2″ squares of substrates are cut tosize.

2. Two ⅛″ wide bus bar strips are soldered to one end of each of the twosubstrates. Wire leads are soldered to bus bars

3. A 2″×1 ¾ rectangular piece of solid polymer electrolyte EK 10 is cutto size (electrolyte thickness=850 μm).

4. The SPE (Solid Polymer Electrolyte) was laid on the first substrate.

5. The substrates and the SPE are assembled with a ¼ offset with the busbars on opposite sides.

6. The assembly is then vacuum sealed in a flexible bag and placed in anautoclave at 130C at 200 psi for 1 hour (typical temperature range isbetween 100 to 180C and the pressure range between 100 to 300 psi).

7. After the autoclave cycle is complete the device is left to stand for24 hours prior to testing.

The impedance was measured by running a frequency scan (Solartron 1260impedance analyzer, Farnborough, Hampshire, England) while measuring thereal and imaginary components of the complex impedance at each frequencypoint. The frequency range was 1 Hz to 100 KHz. The impedance is thenmeasured from the slope and intercept of the complex plane plot.Residual current was measured by subjecting the same device to a forwardvoltage scan at 10 mV/sec at 85C and measuring the current at 1.5 V.

Conductivity, σ Residual σ mS · cm⁻¹ σ mS · cm⁻¹ σ mS · cm⁻¹ Electrolytecurrent A/cm² (20° C.) (0° C.) (−20° C.) EK10 @1.5 V, 85° C. 3.63 × 10⁻⁵1.44 × 10⁻⁵ 1.8 × 10⁻⁶ 1.36 × 10⁻⁶

Photopic transmission was measured using Hunterlabs Ultrascan XEcolorimeter. A 2″×2″ square of SPE is laminated between two transparentsoda-lime glass plates (600μ thick film between two 2.1 mm thicksubstrates) as described above. The laminated assembly is then testedfor color and transmission. The haze value with various electrolytesusing these substrates was in the range of 1.6 to 2.4.

Electrolyte Color Visible Transmission, % EK10 L = 90.06 76.4 a* = −1.98b* = 3.45

EXAMPLE 2

Another clear electrolyte composition which was extruded is describedbelow

Elec- σ mS · cm⁻¹ σ mS · cm⁻¹ σ mS · cm⁻¹ trolyte (20° C.) (0° C.) (−20°C.) EK63 3.6 × 10⁻⁴ 1. × 10⁻⁴ 2 × 10⁻⁵

This consisted of 14% UV stabilized PVB, 14% UV stabilized PMMA, 33%tetraglyme, 4% LiClO4 and 35% SiO2 (all % by weight). The residualcurrent for this film at 85C at 1.5 V was 1.3×10⁻⁶ A/sq. cm. Theelongation to failure of this film was 670% and its strength to breakwas 10 kg/cm². The film thickness was 600 micro-meters. This film whentested for adhesion on tungsten oxide according to ASTM D3167 yielded 30pounds/linear inch width (5.4 kg/linear cm width). The film wassupported by a backing film as the electrolyte film's adhesion exceededthe force that this film could bear before failure.

A laminate was produced with a 0.093 inch thick TEC 15 glass coated with350 nm thick tungsten oxide on the conductive side which was laminatedto a 0.125 inch thick TEC 8 piece of glass coated with 200 nm thickvanadium oxide on the conductive side. Asymmetry in glass thickness isdesirable from a noise and vibration reduction perspective. The laminatesamples which were about 1 sq ft squares were tested for ANSI Z26.1-1996(test 12) using a 0.5 pound ball drop. When the ball was dropped from 15ft, the ball did not penetrate the laminate and no glass pieces biggerthan 1 sq inch were released from the laminate (FIG. 2). When the ballwas dropped from 30 ft, it penetrated the laminate, but no pieces largerthan 1 sq. inch were released from the laminate. The laminate did notshow any signs of visual delamination when stored at −40C and at 120C.

Procedure for Assembling an Electrochromic Device

A TEC 15 substrate (a glass substrate coated with conductive tin oxide)about 7.5 cm×7.5 cm was coated with a tungsten oxide doped with lithiumoxide. The ratio of lithium to tungsten was 0.5. The method ofdeposition was by a wet chemical method (dip coating) as described inAllemand, et al U.S. Pat. No. 6,266,177 issued Jul. 24, 2001 entitledElectrochromic Devices. The coating thickness was 350 nm. The coatingwas etched from the non conductive side of the substrate and also alongthe perimeter, about 5 mm from the substrate edge on the conductiveside. A wet chemical coating was also deposited on another TEC substrateof crystalline vanadium oxide (200 nm thick) and similarly removed fromthe non-conductive side and around the perimeter as described above. Asoldered metal busbar was applied on one of the edges of both substrateson the conductive side. The busbar was about 2 mm wide and located inthe etched but conductive area. A wire was connected to the busbar onthe substrate coated with tungsten oxide. The coated area of thesubstrate was immersed in 1.0 M LiClO₄ in PC. The bath had a stainlesssteel counterelectrode and also a Ag/AgNO₃ reference electrode. Thetungsten oxide was galvanostatically reduced by lithium ions by applyinga charge of 0.032C/cm² of the coated area. The charge depends on thethickness of the two electrodes, their reversal capacities and theircoloration efficiencies, since this charge is shuttled between theelectrodes to color and bleach the EC device. Typically this chargeshould be greater than 0.005C/cm² of the device. The reduction byincorporation of ions in a electrode is typically done by using one ofH, Li, Na and K elements.

Once reduced, the tungsten electrode was rinsed with acetonitrile andblown dry with N₂ and stored under inert atmosphere. Although thecounter electrode, vanadium oxide was not reduced in this process, butthat could have been done instead or both electrodes could have beenpartially reduced. The reduction could be done other thanelectrochemical means, such as chemical methods (exposing one or bothelectrodes to reducing liquids or gasses), photo-chemical orphoto-electrochemical (here radiation, typically UV and/or visible lightis used to catalyze or promote reduction), or even including reducingmaterials in the electrolyte sheet which reduce the electrode in-situduring post processing because of heat and/or by the use of radiation.Reducing agent may even be added to the coating solution so thatreduction and coating are done in one step, more on this is described inU.S. Pat. No. 5,989,717 which is incorporated by reference herein.

The electrolyte sheet was cut to size, this being done preferably in dryand most preferably in dry and inert atmosphere and placed between thetwo substrates where the coated (and for some types of EC devices, atleast one of the surfaces is a reduced layer) face the electrolyticsheet. The substrates are staggered in the busbar areas with the busbaron the two substrates along the two opposite edges, and the sheetpreferably extends only to the coated area (i.e., does not extend on tothe etched area). The assembled device is then sealed in a vacuumdouble-bag (and a vacuum is pulled to degas) and placed in an autoclaveat 130° C. and 200 psi for 1 hr with 45 min ramp time. The pressure ismaintained after the completion of the heating cycle and after thesamples have cooled down to 37° C. or lower. Devices are then taken outof the autoclave and removed from the vacuum bags carefully. It isimportant to verify that the adhesion between the electrodes and theelectrolyte is maintained in both the reduced and the oxidized states.The edges of the substrate are sealed with an adhesive, which is eitherapplied only on the edges or is forced between the two substrates (inthe etched perimeter). To enhance adhesion, the etched areas could beprimed with a suitable material (e.g., a silane based primer) which iscompatible with the adhesive.

Alternatively, the seal is dispensed before the electrolyte islaminated, and then cured or processed along with the heat and/orpressure which is applied to process the laminate. An edge seal in tapeform can be wrapped tightly around the perimeter (Thermedics BOC-9450,Woburn, Mass. or structural bonding tapes from 3M, Minneapolis, Minn.,such as product number 9245) and taped in place using Kapton tape. Theseal as applied is generally loose at the edges, and allows thedegassing to take place, however, when it is heated in the autoclaveunder pressure this melts or softens, and bonds to the periphery. Theseal may even be dispensed on one of the substrate before the assemblyof the two substrates (e.g., a bead from crosslinkable silicones,polysulfides, polyurethanes and butyls such as Del Chem D2000 (fromDelchem, Wilmington, Del.), which may have been treated with a adhesionpromoting primer described above. The seal is cured later (e.g.,crosslinks) in the autoclave or in the lamination process of choice. Toallow degassing before lamination, a break in the seal could be leftwhich can be sealed after lamination, or the sealant may flow in thisarea when heat/and or pressure are applied during lamination. Amechanical device such as a needle may be inserted in this seal fordegassing, which is later removed when heat and/or pressure are laterapplied to complete the lamination process so that the hole left by theneedle is sealed.

Alternatively, a seal in the form of a gasket laid to engulf theperimeter of solid electrolyte film with a minimal gap in between canprovide an additional barrier to environmental transgress with lesslimitation on the seal width. For example, a square piece of electrolytefilm was laminated between two transparent conductors. During thefabrication a square ¼″ thick gasket of polyvinylbutyral (as seal) wascut to fit around the SPE then the assembly was fabricated and laminatedas described above. After the lamination cycle was complete and thesample was allowed to cool, visual inspection of the fabricated deviceshowed a seamless square transparency where the interface between thesealant and the electrolyte was hard to distinguish. Thus, in principle,one could select a material in a sheet form with the desired barrierproperties and good adhesion to substrate, precut it (or stamp out thedesired shape) to fit an EC construction and provide a visuallyappealing clean seal with or without additional edge seals. Someexamples of such materials are ionic polymers such as Surlyn™ fromDupont (Wilmington, Del.), butyl tapes/sheets, B-staged epoxy resintapes/sheets, etc. The sealants may also consist of moisture and oxygenscavengers.

A 3×3 inch EC device was constructed using the electrodes along with thepolymeric film described above which is edge sealed by the Thermedicstape during the lamination process. The device transmission was 45% at550 nm. When a coloring potential of 1.5 V was applied to the device(with the tungsten oxide side negative), the device colored to a 15%transmission in 120 seconds. The device remained in this state for 4days showing that it has good memory. When a bleach potential of −0.6 V(tungsten oxide electrode positive). The device bleached to 45%transmission in 60 seconds.

The above description of the busbar is only given to make the samplegiven below, however, devices with silver frit busbars, stagger freearrangement of substrates and internal busbars can be used as describedin PCT patent application WO01/84230 and U.S. Pat. No. 6,317,248B1 whichis incorporated herein by reference.

What has been described is illustrative of the principles of theinvention. Modifications may be made to further enhance adhesion andmechanical characteristics. For example, an extruded electrolyte sheetcontaining unreacted monomers may be used which are polymerized eitherduring lamination or in post processing by heat or radiation. Furtherand other modifications may be made by those skilled in the art without,however, departing from the spirit and scope of the invention.

What is claimed is:
 1. Chromogenic glazing exhibiting safety impactcharacteristics, comprising: first and second spaced transparent panels,at least one of which is of glass, said first and second transparentpanels each having a front surface and an opposing rear surface, saidrear surface of the first panel facing and spaced from the front surfaceof the said second panel defining a space between the said first andsecond panels, said rear surface of said first panel and said frontsurface of said second panel coated with a transparent conductor; and asolid electrolyte medium disposed in said space which adheres to any ofsaid coated panels with an adherence which exceeds 1.8 kg/linear cmwidth.
 2. Chromogenic glazing according to claim 1 wherein saidelectrolyte medium has a tensile strength of at least 5 kg/cm². 3.Chromogenic glazing according to claim 1 wherein said electrolyte mediumhas an elongation greater than 100%.
 4. Chromogenic glazing according toclaim 1 wherein said transparent conductors is selected from the groupcomprising of Indium-tin oxide and fluorine-doped tin oxide. 5.Chromogenic glazing according to claim 1 wherein said panels include anelectrochromic layer selected from the group comprising of tungstenoxide, molybdenum oxide, and mixed oxides comprising tungsten andmolybdenum.
 6. Chromogenic glazing according to claim 1 wherein saidpanels include an electrochromic layer selected from the groupconsisting of polyaniline and polythiophene.
 7. Chromogenic glazingaccording to claim 1 wherein said panels include an ion storage layerselected from the group consisting of iridium oxide, nickel oxide,manganese oxide and vanadium oxide, titanium-vanadium oxide,titanium-cerium oxide, niobium-vanadium oxide, and mixtures of saidoxides.
 8. Chromogenic glazing according to claim 1 wherein said panelsare soda-lime glass and include at least one of an anti-iridescentcoating and a coating to reduce sodium diffusion.
 9. Chromogenic glazingaccording to claim 1 where the contrast ratio of the electrochromicdevice is greater than 2:1.
 10. Chromogenic glazing according to claim 1where the electrolyte conductivity at 25C is greater than 10⁻⁶ S/cm. 11.Chromogenic glazing according to claim 1 where the electrolyte exhibitsa Tg lower than 0 C.
 12. Chromogenic glazing according to claim 1 wherethe haze of the said glazing is less than 5%.
 13. Chromogenic glazingaccording to claim 1 where the said glazing is UV stable. 14.Chromogenic glazing as in claim 1 having an extruded electrolytic filmselected from the group consisting of poly-acrylates, polystyrenes,polyvinyl butyrals, polyurethanes, poly vinyl acetates, poly vinylchlorides and polycarbonates; a filler selected from the groupconsisting of polymer particles, pyrolitic silicas, aluminas, ceriumoxides and zinc oxides; at least one dissociable salt selected from thegroup consisting of LiClO₄, LiCF₃SO₃, LiN(CF₃ SO₂)₂, and NaCF₃SO₃; atleast one solvent for dissociating said salt selected from the groupconsisting of propylene carbonate, ethylene carbonate, gamma-butyrolactone, and tetraglyme, sulfolane.
 15. Chromogenic glazing according toclaim 14, said film being bonded in situ to the substrates of saidglazing under heat and pressure.
 16. Chromogenic impact resistant safetyglazing, comprising first and second spaced transparent panels, saidfirst and second transparent panels each having a front surface and anopposing rear surface, said rear surface of the first panel facing andspaced from front surface of the said second panel defining a spacebetween the said first and second panels, said rear surface of saidpanel and said front surface of said second panel coated with atransparent conductor wherein the said conductive side of at least oneof the electrodes is further coated with additional layer where at leastone of the said additional layer is reduced; and a solid electrolytemedium disposed in said space, where the adhesion of the saidelectrolyte to any of the said coated panels exceeds 1.8 kg/linear cmwidth.
 17. Chromogenic glazing according to claim 16 where the tensileelongation of the electrolyte to break is greater than is greater than100%.
 18. An electrolyte for glazing assembly as in claim 16 in whichsaid electrolyte has a tensile strength of at least 5 kg/cm². 19.Chromogenic glazing according to claim 16 where the electrolyteconductivity at 25C is greater than 10⁻⁶ S/cm.
 20. Chromogenic glazingaccording to claim 16 where the electrolyte Tg is lower than 0° C. 21.Chromogenic glazing according to claim 16 where the haze of theelectrolyte is less than 5%.
 22. An electrochromic laminate formed bysandwiching an electrolytic layer between two transparent substrates,said laminate reducing sound transmission by at least 3 dB.
 23. Anelectrochromic laminate as in claim 22 which is impact resistant.
 24. Anelectrochromic laminate in claim 23 in which the substrates aredifferent in thickness.